1. Field of the Invention
The present invention relates to an aspherical lens as a refracting and correcting means for eyes, such as an intraocular lens and a contact lens, a method of producing the aspherical lens, and an apparatus for producing the aspherical lens.
2. Description of the Related Art
Conventionally, for example, an intraocular lens is generally designed by expressing asphericity of the intraocular lens in a polynomial of even order showing differences between an aspherical surface thereof and a spherical surface, performing ray tracing while changing a coefficient of the polynomial and calculating an aberration, or by expressing the asphericity in a special algebraic function instead of the polynomial.
However, the above methods are disadvantageous in that an expression of the asphericity is limited to one expressible by an algebraic function and the degree of freedom of design is also restricted.
For example, in the case of a refracting curved surface in rotation symmetry with respect to the optical axis, a radius of curvature of a point is determined by the distance between the point and the optical axis. If the radius of curvature is expressed by a radius of curvature depending on the distance from the optical axis, the radii of curvature of different two points have a regular relationship therebetween depending on the shape of an algebraic function and the radii of the points cannot be separately changed.
Accordingly, the degree of freedom of design is generally restricted in a method which uses an algebraic function to express asphericity, and for example, it is impossible to design an intraocular lens from which entirely removes the spherical aberration, and so on.
In general, since the quality of an image in a fovea of macular region in an eye-ball optical system has an influence on visual acuity, how to control a spherical aberration is one of the most important problems in producing an intraocular lens and a contact lens.